Electrode system



May 19, 1959 P.- J. w. JOCHEMS ET AL ELECTRODE SYSTEM Filed Sept, 5. 1952 I Invenldrs Pieler Jobahnes Mike/mus JOCIMMS leonard' Johan rummcrs United States Patent 2,887,631 ELECTRODE SYSTEM Pieter iohannes willielmus Jochems and Leonard .lohan Tummers, Eindhoven, Netherlands, assignors, by

' mesne .assignments toNorthAmericaii Philips Com.- pany, Inc., New York, N.Y., a corporation of Delaware Application September 5, 1952, Serial No. 308,002

Claims priority, application Netherlands October 6, 1951 2 Claims. (Cl. 317-235) This invention relates to electrode systems comprising a holder to which are secured a semi-conducting electrode and two or more filamentary well conducting electrodes so as to be insulated from each other, the filamentary elec trodes each resting with one end, hereinafter termed the free end, on the surface of the semi-conducting electrode. The other end of the filamentary electrodes, which is secured in the holder, will hereinafter be termed the fixed end. Such an end may be secured directly in an insulating part of the holder. As an alternative, however, it may be secured to a separate conducting support secured, in its turn, to the holder.

In order to confer the desired electric properties on the system it is necessary for the relative spacing of the free ends of the filamentary electrodes to be exactly fixed. This, however, is impeded by the comparatively great length which these electrodes must be given in order to make them resilient. To this end such an electrode is often staggered.

The present invention has, among other things, for its object to provide a construction where the spacing between the free ends is maintained exactly constant.

According to the invention, at least two filamentary electrodes are interconnected by an insulating bridge between their fixed ends and their free ends. Preferably, this bridge is exclusively supported by said electrodes, but it is also possible to give the bridge a separate support.

In an advantageous form of construction, the electrode parts located between the bridge and the fixed ends are curved, whereas the parts between the bridge and the free ends are rectilinear.

In order that the invention may be clearly understood and readily carried into effect, it will now be described in detail with reference to the accompanying drawing given by way of example, in which Fig. 1 is a sectional view of a transistor.

Figs. 2 to 5 illustrate the manufacture of two filamentary electrodes with an insulating bridge in different phases.

Fig. 6 is a sectional view of a different transistor construction.

Fig. 7 is a perspective view of a difierent construction of the insulating bridge.

The transistor generally consists of a holder 1 usually surrounding the electrode as a housing. This holder may consist of a length of tubing, for example of metal or of insulating material such as synthetic resin or glass.

At one end is provided an insulating plug 2 with two metal pins 3 to which the fixed ends 4 of filamentary electrodes 5, 6 are welded. Of course, many variations of this supporting construction are possible.

The semi-conducting electrode 7, for example consisting of germanium, is soldered to a metal pin 8 which is supported by a second insulating plug 9 in the holder 1.

In order that the spacing of the free ends 10, 11 of the filamentary electrodes 5, 6 may be fixed very accurately, an insulating bridge, in the present case in the form of a bead; imntovided. between the: sa d e d and h s ppo 2, 3 ofsaidclectrodes- .1 1

This :bea dlmight consist of glass and be melted around the electrodes, ,Jnconnection, however, with the sensitivity to, heat of these usually very thin wires, preference is: given to, aninsulating substance .capable of being dissolved, for example polystyrene. A drop of this solution may be provided on the electrodes which will maintain their spacing after vaporisation of the solvent. This spacing is previously set, for example in a jig.

A simple method of manufacturing such a system is to make two filamentary electrodes from a single length of wire. This length of wire 13, for example consisting of Phosphor bronze or tungsten may first be bent into the form shown in Fig. 2 and subsequently be given a bend 14 of 180 by bending this wire around a jig 15 shown in section, the wire ends then being welded to two pins 3 secured in an insulating plug 2 (Fig. 3).

Subsequently the insulating bridge or head 12 is provided near the bend 14 (Fig. 4), for example by providing a droplet of a solution of polystyrene in benzene on the wire.

After that the bend 14 is introduced into an etching liquid 16 which may, for example, consist of a solution of 10% of potassium hydroxide iniwater, an alternating voltage being applied between the bath and the wire. After the bend 14 has been entirely etched away, the electrodes have two pointed free ends 10, 11 with the exact predetermined spacing (Fig. 5).

By bending the wire 13 in the aforesaid manner the filamentary electrodes between their support 2, 3 and the insulating bridge, namely the bead 12, will show a number of bends imparting the required resilience to said electrodes.

If this resilience should be acted upon in some manner, the insulating bridge 12 may be furnished with a separate support 17 which may also consist of wire (Fig. 6). In this manner the bead is supported at three points so that lateral displacements are counteracted.

As a rule, the aforesaid construction of the insulating bridge, namely as a bead formed from a droplet, is satisfactory in every respect. In conjunction with the small spacing of the free electrode ends, which is usually of the order of 11., the bridge can be made very small.

As an alternative, the insulating bridge may partly consist of conducting parts, for example of two metal Wires 18, 19 and an insulating bead 20 as shown in Fig. 7. This bead may in turn be separately supported by a wire 21. The wires 18, 19 are welded to the free ends 10, 11 of the filamentary electrodes.

The free ends of the filamentary electrodes will generally have about the same length. If there should be a small difference in length, for example due to the etch ing operation, this difference will not cause trouble, since the bridge may occupy a slightly oblique position. It may even be advantageous to produce a dilference in length intentionally in order that the pressure exerted by one electrode on the semi-conductor may exceed that exerted by the other electrode. In a transistor, the electrodes have difierent functions and it may be of importance to give one of them a higher pressure than the other, or conversely.

What we claim is:

1. A semi-conductor translating device comprising a holder, a body of semi-conductive material having a free surface and secured in a portion of said holder, means effecting electrical connection to said semi-conductive body, a pair of spaced insulated resilient filamentary electrodes having fixed ends secured to said holder and pointed free ends in pressure engagement with said free surface of said semi-conductive body, and an insulating bridge Patented May 19, 1959 3 4 secured to said pair of filamentary electrodes at a position 2. A semi-conductor translating device as claimed in completely between the fixed and the free ends thereof claim 1 in which the insulating bridge is constituted by a and spaced from said semi-conductive body and said polystyrene bead. holder and defining the spacing between the electrodes, the portion of said electrodes between the bridge and the 5 References Cited in the file of this P511611t free ends thereof being rectilinear and parallel to one another, the portion of said electrodes between the bridge UNITED STATES PATENFIS and the fixed ends thereof being curved to impart the 2,538,593 Rose Jan. 16, 1951 requisite pressure of engagement of said free ends to said 2,606,960 Little Aug. 12, 1952 body. 10 2,608,722 Stuetzer Sept. 2, 1952 

